The use of vaccines to prevent diseases in humans, farm livestock, sports animals and household pets is a common practice, and considerable effort has been, and is being, made to extend this practice to cover a more extensive array of diseases to which these patients are subject. For example, the use of rabies vaccine in animals is by now commonplace, and efforts are being made to obtain suitable vaccines to immunize animals against other diseases.
One problem that frequently is encountered in the course of active immunization is that the antigens used in the vaccine are not sufficiently immunogenic to raise the antibody titer to sufficient levels to provide protection against subsequent challenge or to maintain the potential for mounting these levels over extended time periods. Another problem is that the vaccine may be deficient in inducing cell-mediated immunity which is a primary immune defense against bacterial and viral infection.
In order to obtain a stronger humoral and/or cellular response, it is common to administer the vaccine in a formulation containing an adjuvant, a material which enhances the immune response of the patient to the vaccine. The most commonly used adjuvants for vaccines are oil preparations and alum. The mechanisms by which such adjuvants function are not understood, and whether or not a particular adjuvant preparation will be sufficiently effective in a given instance is not predictable.
In addition, with the advent of gene therapy it has been reported that some success has been accomplished with using genes or "naked DNA" as vaccines. However, as with some of the conventional vaccines, the immune response obtained was insufficient to afford immunization.
Accordingly, there is a need for additional effective adjuvant preparations which are suitable for potentiating vaccines for animals in general, and particularly in humans.